Electrical contacts are extensively used in modern electronic equipment. Gold is particularly suitable as an electrical contact material because of its excellent conductivity properties, its chemical inertness and relative availability compared to other noble metals. In addition, gold can be put down in the form of film on surfaces using a large variety of relatively simple processes. For example, gold can be electrolessly plated onto catalytic surface metals and also electroplated onto various suitable metallic surfaces. In addition, gold can be sputtered or evaporated to form films suitable for electrical contacts.
The main advantages of gold in contact applications are good electrical conductivity and chemical inertness. Chemical inertness prevents a gold from forming an oxide film which would make good electrical contact difficult. Because of these two favorable properties of gold, gold contacts can be made with extremely small contact resistance. Also, the contacts are not degraded by exposure to corrosive atmospheres over long periods of time.
In some electrical contact applications, it is desirable to have the gold contact surface in the form of spongy gold rather than dense gold. Such structures have been mentioned in the literature (Ch. J. Raub et al, Journal of the American Electroplator's Society, Plating and Surface Finishing Volume 63, Number (January 1976) page 35. Producing such spongy gold surfaces requires a heat treatment which is often detrimental to the contact device being fabricated. Such processes often involve high temperatures which adversely affect certain types of magnetic materials used in magnetic contact reeds. In addition, it would be economically advantageous to be able to carry out the process without a vacuum and over a shorter period of time. For this reason, it is advantageous to develop processes for rendering gold surfaces spongy which do not adversely affect other parts of the contact device.